Photoconductive elements containing polymeric binders

ABSTRACT

PHOTOCONDUCTIVE ELEMENTS CONTAINING A PHOTOCONDUCTOR AND BINDER FOR THE PHOTOCONDUCTOR COMPRISING A CERTAIN CLASS OF POLYESTERS HAVING ARYLENEOXY REPEATING UNITS ARE DESCRIBED. THE DESCRIBED ELEMENTS CAN BE SENSITIZED AND CHARGED EITHER NEGATIVELY OR POSITIVELY AND USED TO PREPARE IMAGES ELECTOPHOTOGRAPHICALLY.

United States Patent US. Cl. 96-1.6 12 Claims ABSTRACT OF THE DISCLOSURE Photoconductive elements containing a photoconductor and binder for the photoconductor comprising a certain class of polyesters having aryleneoxy repeating units are described. The described elements can be sensitized and charged either negatively or positively and used to prepare images electrophotographically.

This is a continuation of application Ser. No. 779,201 filed Nov. 26, 1968 and now abandoned.

This invention relates to novel electrophotographic elements having coatings of binder-containing photoconductive compositions.

Binder-containing photoconductive compositions have been widely used in the preparation of electrophotographic elements. In electrophotographic reproduction processes, these elements are utilized in the formation of latent electrostatic images. In some applications the photoconductive compositions contain an organic photoconductor and a sensitizer uniformly admixed in an inert resinous binder. Many binders are currently used in connection with a wide variety of available organic photoconductor compounds and compositions. Typical binders are ordinary polymeric materials, e.g., phenolic resins, ketone resins, acrylic ester resins, polystyrene, etc. However, these binders usually do not impart any particular improvement in light sensitivity to the system. The light sensitivity as indicated by the electrical speed of these particular systems is ordinarily due wholly to the organic photoconductor and sensitizer. Other binders have been found to contribute significantly to the light sensitivity of the system. However, the selection of these polymers for incorporation into photoconductive compositions to form electrophotographic layers has proceeded on a compound-by-compound basis. Nothing has yet been dis covered from the numerous binders tested which permits A L M effective prediction and selection of particular polymers exhibiting the desired properties.

It is, therefore, an object of this invention to provide improved novel binder-containing photoconductive compositions which exhibit high light sensitivities.

It is another object to provide transparent electrophotographic elements having the high speed characteristic of the novel photoconductive compositions of this invention.

These and other objects of this invention are accomplished by a photoconductive composition which contains a photoconductor admixed with a binder therefor which is a copolyester having one of the structures set forth below. It has been discovered that such compositions exhibit increased light sensitivities as evidenced by greater speeds. In particular, substantial increases in speeds are obtained as compared to speeds attainable with many other polymeric binder compositions. These increases in speed are observed when the coating accepts a suitable potential (e.g., 500-600 volts) and the relative speed of the coating is determined on the basis of the reciprocal of the exposure required to reduce the potential of the surface charge by 1 00 volts (shoulder speed) or to volts (toe speed). The reduction of the surface potential to 100 volts or below is significant in that it represents a requirement for suitable broad area development of a latent image. The relative speed at 100 volts is a measare of the ability to produce and henceforth to develop or otherwise utilize the latent image. When the photoconductor is absent from the coating and only a conventional binder is used, the surface potential does not drop to or below 100 volts and therefore no speed can be assigned to such a composition. When a photoconductor is part of the coating in many conventional polymeric binders, the surface potentials of such resultant compositions usually drop below 100 volts, and thus, a definite speed can be ascertained. However, these speeds are improved when the binders of this invention are employed.

The copolyester binders of this invention include those having repeating unit A together with either repeating unit B, C, D, E or F, i.e., a given polymeric molecule has repeating units of A and B, or A and C, or A and D, etc. Additionally, the copolyesters useful as binders in the invention can have repeating units of A together with any combination of B, C, D, E and F, e.g., A with B and E, or A with C and D, or A with E and F, etc. The repeating units referred to thus far have the following structures:

I u Tomcat-Q-+--o-crnom-o-o-xwherein:

D can be (1) An aliphatic alkyl radical having 1 to 8 carbon atoms including a substituted alkyl radical such as haloalkyl, aralkyl, etc., e.g., methyl, ethyl, propyl, butyl, chloromethyl, trifiuoromethyl, benzyl, etc.;

(2) An aryl radical including a substituted aryl radical such as alkaryl, haloaryl, etc., e.g., phenyl, naphthyl, bromophenyl, tolyl, dichloronaphthyl, trimethylphenyl, etc.;

(3) Joined with J to complete a substituted or unsubstituted fused ring moiety with the adjacent phenylene group on which J is substituted, there being 9 to 10 carbon atoms in the resultant fused ring nucleus such as an indanylene nucleus, a naphthylene nucleus, a methyl indanylene nucleus, etc.;

(4) Joined with E to complete a monocycloalkylidene nucleus having 4 to 7 carbon atoms in the nucleus including a substituted cycloalkylidene nucleus such as a cyclobutylidene nucleus, cyclopentylidene nucleus, a cyclohexylidene nucleus, a methyl cyclohexylidene nucleus, a dichlorocyclohexylidene nucleus, etc.;

(5 Joined with E to complete a substituted or unsubstituted bridged cycloalkylidene group having two or three bridges and typically having about 5 to 20 carbon atoms such as a bicyclohexylidene radical, a bicyclopentylidene radical, a norpinylidene radical, a norcarylidene radical, a norbornylidene radical, a thujylidene radical, a pinylidene radical, a carylidene radical, a norbornylidene radical, etc.;

(6) A cycloalkyl radical including a substituted cycloalkyl radical having 4 to 7 carbon atoms in the cycloalkyl nucleus, e.g., cyclobutyl, cyclohexyl, cycloheptyl, methylcyclohexyl, chlorocyclohexyl, etc.;

E can be any of the substituents set forth above for D or hydrogen;

G. J, L, M, G, J, L, and M each can be (1) An aliphatic alkyl radical preferably having 1 to 8 carbon atoms including a substituted alkyl radical such as haloalkyl, aralkyl, etc., e.g., methyl, ethyl, butyl, chlorobutyl, benzyl, etc.;

(2) A hydrogen atom;

(3) A halogen atom;

(4) A cycloalkyl radical including a substituted cycloalkyl radical having 4 to 7 carbon atoms in the cycloalkyl nucleus, e.g., cyclobutyl, cyclohexyl, cycloheptyl, etc.;

Z is an alkylene radical having 2 to 10 carbon atoms including a substituted alkylene radical such as (a) a straight chain or branched chain alkylene hydrocarbon radical, e.g., a trimethylene radical, a tetramethylene radical, a pentamethylene radical, a neopentylene radical, an ethylene radical, a hexamethylene radical, a propylene radical, etc. (b) an oxydialkylene radical or a thiadialkylene radical, e.g., an oxydiethylene radical, a thiadiethylene radical, etc., (c) an alkylene bis(oxyalkylene) radical or an alkylene bis(thiaalkylene) radical, e.g., a methylene bis(oxyethylene) radical, an ethylene bis(thiamethylene) radical, an ethylene bis (oxyethylene) radical, etc., or (d) a cycloalkylene hydrocarbon radical, e.g., a cyclohexylenedimethylene radical, a cyclopentylenedimethylene radical, a cyclobutylenedimethylene radical, a cyclobutylene-diethylene radical, a cyclobutylene radical, a 2,2,4,4- tetramethylene-1,3-cyclobutylene radical, etc.;

Q represents the atoms necessary to complete a substituted or unsubstituted 4 to 7 membered cycloalkylene nucleus, e.g., a cyclobutylene nucleus, a cyclopentylene nucleus, a dialkyl substituted cyclohexylene nucleus, etc.;

R is an alkylene radical having 2 to 10 carbon atoms including a branched chain alkylene radical, e.g., an ethylene radical, a propylene radical, a trimethylene radical, a tetramethylene radical, etc.;

R is an alkylene radical having 3 to 10 carbon atoms including a branched chain alkylene radical, e.g., a propylene radical, a trimethylene radical, a tetramethylene radical, etc.;

D can be (1) An aliphatic alkyl radical having 2 to 8 carbon atoms including a substituted alkyl radical such as haloalkyl, aralkyl, etc., e.g., ethyl, propyl, butyl, chloroethyl, trifluoroethyl, etc.;

(2) An aryl radical including a substituted aryl radical such as alkaryl, haloaryl, etc., e.g., phenyl, naphthyl, bromophenyl, tolyl, dichloronaphthyl, trimethylphenyl, etc.;

(3) Joined with J to complete a substituted or unsubstituted fused ring moiety with the adjacent phenylene group on which J is substituted, there being 9 to 10 carbon atoms in the resultant fused ring nucleus such as an indanylene nucleus, a naphthylene nucleus, a methyl indanylene nucleus, etc.;

(4) Joined with E to complete a monocycloalkylidene nucleus having 4 to 7 carbon atoms in the nucleus, including a substituted cycloalkylidene nucleus such as a cyclobutylidene radical, a cyclopentylidene radical, a cyclohexylidene radical, a methylcyclohexylidene radical, a dichlorocyclohexylidene radical, etc.;

(5 Joined with E to complete a substituted or unsubstituted bridged cycloalkylidene radical having two or three bridges and typically having about 5 to 20 carbon atoms such as a bicyclohexylidene radical, a bicyclopentylidene radical, a norpinylidene radical, a norcarylidene radical, a norbornylidene radical, a thujylidene radical, a pinylidene radical, a carylidene radical, a norbornylidene radical, etc.

J" can be (1) An aliphatic alkyl radical preferably having 1 to 8 carbon atoms including a substituted alkyl radical such as haloalkyl, aralkyl, etc., e.g., methyl, ethyl, butyl, chlorobutyl, benzyl, etc.;

(2) A halogen atom;

(3) A cycloalkyl radical including a substituted cycloalkyl radical having 4 to 7 carbon atoms in the cycloalkyl nucleus, e.g., cyclobutyl, cyclohexyl, cycloheptyl, etc.;

X can be an arylene radical including a substituted arylene radical and preferably a phenylene radical joined in the polymer chain in the l and 3 or 1 and 4 positions of the phenylene radical, for example, a phenylene radical, an alkyl substituted phenylene radical, a halo-substituted phenylene radical, a naphthylene radical, an alkoxy substituted phenylene radical, an aryloxy substituted phenylene radical, an aryl substituted phenylene radical, etc.

The copolyester binders of this invention suitably contain 2 to 80% and preferably 30 to 60% of repeating unit A. The binder also suitably contains from about 20 to 98% and preferably 40 to 70% of repeating unit B, C, D, E or F, or any combination thereof. The polymer contains these units arranged in a random, linear fashion. Binders comprising such polymers improve the electrical speed of the photoconductive composition.

Exemplary of a few of the many polymers useful as binders in this invention are listed in the following Table I.

TABLE I (1 Poly (4,4'-isopropylidenebisphenoxypropyl-coethylene terephthalate) p (2) Poly(4,4-cyclopentylidenebisphenoxyethyl-coethylene terephthalate) (3) Poly(4,4'-isopropylidenebisphenoxy-lrmethylethyl-co-ethylene terephthalate) I (4) Poly(4,4'-isopropylidenebis-Z-methylphenoxyethyl-co-ethylene terephthalate) (5 Poly[4,4'-( l-phenylethylidene)bisphenoxy-ethylco-ethylene terephthalate] (6) Po1y[4,4-( 2-norbornylidene)bisphenoxyethyl-coethylene terephthalate] (7 Po1y{4,4f 1-(p-bromophenyl)ethylidene1bisphenoxyethyhco-ethylene terephthalate} (8) Poly(4,4'-hexafluoroisopropylidenebisphenoxyethyl-co-tetramethylene isophthalate) (9) Poly[3-ethyl-2-methyl-6-indanyloxyethyl-1-(4- phenoxyethyl)-co-ethylene terephthalate] 10) Poly [4,4(4-methylcyclohexylidene bis-Z-methylphenoxyethyl-co-ethylene terephthalate] 1 1) Poly (4,4'-cyclohexylidenebisphenoxyethyl-coethylene terephthalate) (12) Poly(4,4'-benzylidenebisphenoxyethyl-co-ethylene terephthalate) 13 Poly (4,4'-cyclopentylidenebis-2-methylphenoxyethyl-co-ethylene terephthalate) (14) Poly (4,4'-p-menthanebisphenoxyethyl-co-ethylene terephthalate) (15) Poly(4,4'-isopropylidenebis-2,6-dichlorophenoxyethyl-co-ethylene terephthalate) (16) Poly(4,4-isopropylidenebis-2,6-dibromophenoxy ethyl-co-ethylene terephthalate) e (17) Poly[4,4'-( l-isobutylethylidene)bisphenoxyethyl-co-ethylene terephthalate] 18) Poly [4,4'- (hexahydro-4,7-methanoindan-5-ylidene bisphenoxyethyl-co-ethylene terephthalate] 19) Poly [4,4'-( l-cyclohexylethylidene bisphenoxyethyl-co-ethylene terephthalate] (20) Poly(4,4-isopropylidenebis-2-cyclohexylphenoxyethyl-co-ethylene terephthalate) (21) Poly(4,4-isopropylidenebis-2-phenylphenoxyethylco-ethylene terephthalate) I (21a) Poly(4,4-ethylidenebisphenoxyethyl-co-ethylene terephthalate) In preparing typical electrophotographic elements utilizing the polymeric binders of this invention, a photoconductor is dissolved in a solution of binder and solvent and then, after thorough mixing, the composition is coated on an electrically conducting support in a well-known manner, such as swirling, spraying, doctor blade coating, and the like. v

The novel binders of this invention improve the electrical speeds of compositions containing a wide variety of photoconductors including inorganic photoconductors such as zinc oxide, titanium dioxide, cadmium sulfide and the like and organicphotoconductors including organometallic photoconductors. r Typical photoconductors useful with the binders of this invention are described below.

(A) Arylar nine photoconductors including substituted 6 and unsubstituted arylamines, diarylamines, nonpolymeric triarylamines and polymeric triarylamines such as those described in US. Patents 3,240,597 and 3,180,730. (B) Photoconductor represented by the formula wherein A represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear (e.g. phenyl. naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, pentoxy, etc.), or a nitro group; A represents a mononuclear or polynuclear monovalent or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from 1 to about 6 carbon atoms( e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitro group; Q can represent a hydrogen atom or an aromatic amino group, such as A'NH; b represents an integer from 1 to about 12, and L represents a hydrogen atom, a mononuclear or polynuclear aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly(4'-vinylphenyl) group which is bonded to the nitrogen atom by a carbon atom of the phenyl group, these materials being more fully described in US. Patent 3,265,496.

(C) Polyarylalkane photoconductors including leuco bases of diaryl or triarylmethane dye salts, 1,1,1-triarylalkanes wherein the alkane moiety hasat least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials; and also other polyarylalkanes included by the formula:

wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent, the aryl groups attached to the central carbon atom being preferably phenyl groups, although naphthyl groups can also be used including substituted aryl groups containing substituents such as alkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy, halogen, etc. in the ortho, meta or para positions, ortho-substituted phenyl being pre ferred; the aryl groups can also be joined together or cyclized to form a fiuorene moiety, for example; the amino substituent can be represented by the formula wherein each R can be an alkyl group typically having 1 to 8 carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having 5 to 6 atoms in the ring such as morpholino, pyridyl, pyrryl, etc.; at least one of D, E and G preferably being a p-dialkylaminophenyl group, when J is 'an alkyl group, such an alkyl group more generally has 1 to 7 carbon atoms, these materials being more fully described in U.S. Patent 3,274,000, French Patent 1,383,461 and in U.S. Ser. No. 627,857 filed Apr. 3, 1967 by Sens and Goldman, now U.S. 3,542,544.

(D) Photoconductors comprising 4-diarylamino-substituted chalcones having the formula:

wherein R and R are each phenyl radicals including substituted phenyl radicals, R preferably having the formula wherein R and R are each aryl radicals, aliphatic residues of 1 to 12 carbon atoms such as alkyl radicals preferably having 1 to 4 carbon atoms, or hydrogen; particularly advantageous results being obtained when R is a phenyl radical including a substituted phenyl radical and where R is diphenylaminophenyl, dimethylarninophenyl or phenyl, these materials being more fully described in Fox application U.S. Ser. No. 613,846 now U.S. 3,526,501.

(E) Non-ionic cycloheptenyl compounds which may be substituted with substituents such as (a) an aryl radical including substituted as well as unsubstituted aryl radicals, (b) a hydroxy radical, (c) an azido radical,

(d) a heterocyclic radical having 5 to 6 atoms in the heterocyclic nucleus and at least one hetero nitrogen atom, and including substituted and unsubstituted hetero cyclic radicals, and (e) an oxygen linked cycloheptenyl moiety. The substitution on the cycloheptenyl nucleus occurs at an unsaturated carbon atom when the cycloheptenyl moiety is a conjugated triene with no aromatic structure fused thereto. However, if there is at least one aromatic structure fused to the cycloheptenyl moiety, then the substituents are attached to a saturated carbon atom. Additional photoconductors within this class are included in one of the following formulae:

where E and G can be either:

D can be any of the substituents defined for E and G above and is attached to a carbon atom in the cycloheptenyl nucleus having a double bond; (R and R (R and R (R and R and (R and R are together the necessary atoms to complete a benzene ring fused to the cycloheptenyl nucleus; these compounds being more fully described in U.S. Ser. No. 654,091, filed July 18, 1967, now U.S. 3,533,786.

(F) Compounds containing a N--N nucleus including (1) unsubstituted and substituted N,N-bicarbazyls containing substituents in either or both carbazolyl nuclei such as (a) An alkyl radical including a substituted alkyl radical such as a haloalkyl or an alkoxyalkyl radical,

(b) A phenyl radical including a substituted phenyl radical such as a naphthyl, an arninophenyl or a hydroxyphenyl radical,

(c) A halogen atom,

(d) An amino radical including substituted as well as unsubstituted amino radicals such as an alkylamino or a phenylalkylamino radical,

(e) An alkoxy radical,

(f) A hydroxyl radical,

(g) A cyano radical,

(h) A heterocyclic radical such as a pyrazyl, a carbazolyl or a pyridyl radical;

or (2) tetra-substituted hydrazines containing substituents which are substituted or unsubstituted phenyl radicals, or heterocyclic radicals having 5 to 6 atoms in the hetero nucleus, suitable results being obtained when all four substituents are not unsubstituted phenyl radicals, i.e., if at least one substituent is a substituted phenyl radical or a heterocyclic radical having 5 to 6 atoms in the hetero nucleus. Other tetra-substituted hydrazines include those having the following formula:

wherein D E G and I, are each either (a) A substituted phenyl radical such as a naphthyl radical, an alkylphenyl radical, a halophenyl radical, a hydroxyphenyl radical, a haloalkylphenyl radical or a hydroxyalkylphenyl radical or (b) A heterocyclic radical such as an imidazolyl radical, a furyl radical or a pyrazolyl radical. In addition, J and E can also be (0) An unsubstituted phenyl radical. Especially preferred are those tetra-substituted hydrazines wherein both D and G are either substituted phenyl radicals or heterocyclic radicals. These compounds are more fully described in U.S. Ser. No. 673,962, filed Oct. 9, 1967, now U.S. 3,542,546.

(G) Organic compounds having a 3,3-bis-aryl-2- pyrazoline nucleus which is substituted in either fivemember ring with the same or dilferent substituents. The 1 and 5 positions on both pyrazoline rings can be substituted by an aryl moiety including unsubstituted as well as substituted aryl substituents such as alkoxyaryl, alkaryl, alkaminoaryl, carboxyaryl, hydroxyaryl and haloaryl. The 4 position can contain hydrogen or unsubstituted as well as substituted alkyl and aryl radicals such as alkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl, alkoxyalkyl, aminoalkyl, carboxyaryl, hydroxyalkyl and haloalkyl. Other photoconductors in this class are represented by the following structure:

wherein:

D D 1;; and J can be either a phenyl radical including a substituted phenyl radical such as a tolyl radical or a naphthyl radical including a substituted naphthyl radical,

E E G G L and L can be any of the substituents set forth above and in addition can be either a hydrogen atom or an alkyl radical containing 1-8 carbon atoms. These organic photoconductors are more fully described in U.S. Ser. No. 664,642, filed Aug. 31, 1967, now U.S. 3,527,602.

(H) Tiarylamines in which at least one of the aryl radicals is substituted by either a vinyl radical or a vinylene radical having at least one active hydrogen-containing group. The phrase vinylene radical includes substituted as well as unsubstituted vinylene radicals and also includes those radicals having at least one and as many as three repeating units of vinylene groups such as {CH=CH-) wherein n is an integer of from one to three. Groups which contain active hydrogen are well known in the art, the definition of this term being set forth in sveral textbooks such as Advanced Organic Chemistry, R. C. Fuson, pp. 154157, John Wiley & Sons, 1950. The term active hydrogen-containing groups as used herein includes those compounds encompassed by the discussion in the textbook cited above and in addition include those compounds which contain gorups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups substituted on the vinylene radical of the triarylamine include:

(a) Carboxy radicals,

(b) Hydroxy radicals,

(e) Ethynyl radicals,

(d) Ester radicals, (e.g.,

wherein R is alkyl or aryl) including cyclic ester radicals (e.g.,

ll c-o1 etc.), and

(i) Amido radicals (e.g.,

,Rrs

wherein R is a hydrogen atom, an alkyl group or an aryl group). Other active hydrogen-containing groups include substituted and unsubstituted alkylidyne oximido radicals. Photoconductors included in this class can be represented by the following structure:

Ar\1 NAr=(( :=o ).-x

Ar: Rio Rn wherein:

(a) Ar and Ar are each a phenyl radical including a substituted phenyl radical such as a halophenyl radical, an alkyl phenyl radical or an aminophenyl radical;

(b) Ar is an arylene radical including a substituted arylene radical such as a phenylene radical or a naphthylene radical,

(0) R and R are each hydrogen, a phenyl radical including a substituted phenyl radical or a lower alkyl radical preferably having 1--8 carbon atoms;

(d) X is either (1) an active hydrogen-containing group such as carboxyl radical, an acyl halide radical, an amido radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a hydroxy radical, a semicarbazono radical, an ethynyl radical, or a methylidyne oximido radical, or (2) hydrogen, provided that when X is hydrogen R and R are also hydrogen;;and

(e) n is an integer of one to three.

The arylene nucleus can be substituted in any position by the vinyl or vinylene moiety. However, when Ar is phenylene, particularly good results are obtained ifthe substitution occurs in the para position. These materials are more fully described in U.S. Ser. No. 706,800 filed February 20, 1968 now US. 3,567,450.

(I) Triarylamines in which at least one of the aryl radicals is substituted by an active hydrogen-containing group. The term active hydrogen-containing group has the same meaning as set forth above and again includes those compounds encompassed by the discussion in the textbook and additionally includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups which are substituted on an aryl radical of the triarylarnine include:

(a) Carboxyl radicals;

(b) Hydroxy radicals;

(c) Ethynyl radicals;

(d) Ester radicals (e.g.,

wherein R is an alkyl or an aryl group);

(e) Lower alkylene hydroxy radicals (e.g., having 1-8 carbon atoms);

(f) Carboxylic acid anhydride radicals;

(g) Lower alkylene carboxy radicals (e.g., having 2- 8 carbon atoms);

' (h) Cyano radicals;

(i) Acyl halide radicals (e.g.,

etc);

(j) Amido radicals (e.g.,

n -C-N wherein R is a hydrogen atom, an alkyl group or an aryl group);

(k) Lower alkylidyne oximido radicals having l-8 carbon atoms including substituted alkylidyne oximido radicals (e.g.,

wherein R is hydrogen or a lower alkyl radical;

(l) Semicarbazono radicals; and

(m) Arylene carboxy radicals including substituted arylene car-boxy radicals (e.g.,

wherein D and B are phenyl or lower alkyl radicals. Photoconductors included in this class can be represented by the following structure:

wherein:

(a) An, and Ar;, are each a phenyl radical including a substituted phenyl radical such as a halophenyl radical, an alkyl phenyl radical or an amino phenyl radical;

(b) Ar iszan'arylene radical including a substituted arylene radical such as a phenylene radical or a naphthylene radical; and

(c) X is an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amide radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a Semicarbazono radical, a hydroxy radical, an ,ethynyl radical, a methylidyne oximido radical or a phenylene carboxy radical. These materials are more fully described in U.S. Ser. No. 706,780 filed Feb. 20,

(I) Organo-metallic compounds having at least one amino-aryl substituent attached to a Group lVa or Group Va metal atom. The metallic substitutents of this class of organic photoconductors are Group IVa or Group Va metals in accordance with the Periodic Table of the Elements (Handbook of Chemistry and Physics, 38th edition, pp. 394-95) and include silicon germanium, tin and lead from Group IVa and phosphorus, arsenic, antimony and bismuth from Group Va. These materials can be substituted in the metallo nucleus with a wide variety of substituents but at least one of the substituents must be an amino-aryl radical. The amino radical can be positioned anywhere on the aromatic nucleus, but best results are obtained if the aryl moiety is a phenyl radical having the amino group in the 4 or para position. Typical substituents attached to metal nucleus include the following:

[TArl\ d. M52

where E G L and Q can be (a) A hydrogen atom,

(b) An aryl radical including unsubstituted as well as substituted aryl radicals such as a phenyl radical, a naphthyl radical, a dialkylaminophenyl radical, or a diarylaminophenyl radical,

(c) An alkyl radical having 1 to 8 carbon atoms,

'(d) An alkoxy radical having 1 to 8 carbon atoms,

(e) An aryloxy radical such as a phenoxy radical,

(f) An amino radical having the formula wherein R and R can be hydrogen atoms or alkyl radicals having 1 to 8 carbon atoms, or

(g) A heterocyclic radical having 5 to 6 atoms in the hetero nucleus including at least one nitrogen atom such as a triazolyl, a pyridyl radical, etc.;

T is an amino radical such as an alkylamino radical 12 having 1 to 8 carbon atoms or an arylamino radical such as a phenylamino radical;

Ar is an aromatic radical such as phenyl or naphthyl;

M and M are the same or different Group IVa metals;

M is a Group Va metal;

D can be any of the substituents set forth above for E G L and Q and in addition can be a group IVa organo-metallic radical or when taken with B, an oxygen atom or a sulfur atom;

J can be any of the substituents set forth above for E G L and Q and in addition can be when taken with E, an oxygen atom or a sulfur atom. These materials are described in U.S. Ser. No. 650,664, filed July 3, 1967, now Pat. No. 3,647,429.

(K) Any other organic compound which exhibits photoconduoitve propenties suoh as those set forth in Australian Patent 248,402.

Representative organic photoconductors useful in this invention include the compounds listed below:

TABLE I diphenylamine dinaphthylamine N,N'-diphenylb enzidine N-phenyll-naphthylamine N-phenyl-Z-naphthylamine N,N'- diphenyl-p-phenylenediamine 1-carboxy-S-chloro-4-methoxydiphenylamine p-anilinophenol N,N-di-2-naphthyl-p-phenylenediamine 4,4-b enzylidene-bis- (N,N-dimethyl-m-toluidine) triphenylamine N,N,N',N-tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine 4-hexanoyltriphenylamine 4-l anroyltriphenyl amine 4-hexyltriphenylamine 4-dodecyltriphenylamine 4,4-bis( diphenylamino benzil 4,4'-bis (diphenylamino) benzophenone poly [N,4-(N,N',N'-triphenylbenzidine) polyadipyltriphenylamine polysebacyltriphenylamine polydecamethylenetriphenylamine po1y-N-( 4-vinylphenyl) diphenylamine poly-N- (vinylphenyl -a,a'-dinaphthylamine 4,4'-ber1zylidine-bis'( N,N-diethyl-m-toluidine) 4', "-diamino-4-dimethylamino-2,2"-dimethyltriphenylmethane 4,4-bis (diethylamino -2, 6-dichloro-2',2"-dimethyltriphenylmethane 4,4"-bis( diethylamino) -2',2-dimethyldiphenylnaphthylmethane 2,2"-dimethyl-4,4',4"-tris dimethylamino) triphenylmethane 4',4"-bis (diethylamino -4-dimethylamino-2',2"-dimethyltriphenylmethane 4',4"-bis(diethylamino) -2-chloro-2,2"-dimethyl- 4-dimethylaminotriphenylmethane 4,4"-bis(die thylamino)-4-dimethyla1rrino-2,2',2"-

trimethyltriphenylmethane 4,4"-bis (dimethylamino) -2-chloro-2',2"-dimethyltriphenylmethane 4', "-bis (dimethylamino) -2,2"-dimethyl-4-methoxytriphenylmethane Bis (4-diethylamino) -1, 1,1-triphenylethane Bis l-diethylamino tetraphenylmethane 4',4"-bis (benzylethylamino -2',2"-dimethyltripheny1- methane 4, "-bis diethylamino -2,2"-diethoxytriphenylmeth ane 4,4-bis(dimethylamino)-1,1,l-triphenylethane 1-(4-N,N-dimethylaminophenyl)-1,1-diphenylethane 4-dimethylaminotetraphenylmethane 4-diethylaminotetraphenylmethane diphenyl-p-diethylaminophenylsilane p-diethylaminophenylarsine tetrakis- [diphenyl- (p-diethylaminophenyl) plumbyl] methane tetrakis- [diphenyl- (p-diethylaminophenyl stannyl] stannane bis- [phenyl- (p-diethylaminophenyl) Jdibismuthine tri-(p-diethylaminophenyl)phosphine sulfide di- (p-diethylaminophenyl thioxotin The photoconductive layers of the invention can also be sensitized by the addition of effective amounts of sensitizing compounds to exhibit improved electrophotosensitivity. Sensitizing compounds useful with the photoconductive compounds of the present invention can be selected from a wide variety of materials, including such materials as pyrylium including thiapyrylium and selenapyrylium dye salts disclosed in Van Allan et al. U.S. Pat. 3,250,615; fluorenes, such as 7,12 dioxo 13 d-ibenzo(a,h)fiuore'ne 5,10-dioxo4a,1l-diazabenzo(b)fiuorene, 3,13 dioxo-7- oxadibenzo(b,g)fluorene, and the like; aromatic nitro compounds of the kinds described in U.S. Pat. 2,610,120; anthrones like those disclosed in U.S. Pat. 2,670,284; quinones, U.S. Pat. 2,670,286; benzophenones U.S. Pat. 2,670,287; thiazoles U.S. Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, dichloroacetic acid, and salicyclic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine (including carbocyanine), mercocyanine, diarylmethane, thiazine, azine, oxazine, xanthene, phthalein, acridine, azo, anthraquinone dyes and the like and mixtures thereof. The sensitizers preferred for use with the compounds of this invention are selected from pyrylium including selenapyrylium and thiapyrylium salts, and cyanine including carbocyanine dyes.

Where a sensitizing compound is employed with the binder and organic photoconductor to form a sensitized electrophotographic element, it is the normal practice to mix a suitable amount of the sensitizing compound with the coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed in the coated element. Other methods of incorporating the sensitizer or the effect of the sensitizer may, however, be employed consistent with the practice of this invention. In preparing the photoconductive layers, no sensitizing compound is required to give photoconductivity in the layers which contain the photoconducting substances, therefore, no sensitizer is required in a particular photoconductive layer. However, since relatively minor amounts of sensitizing compound give substantial improvement in speed in such layers, the sensitizer is preferred. The amount of sensitizer that can be added to a photoconductorincorporating layer to give effective increases in speed can vary widely. The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 30 percent by weight based on the weight of the film-forming coating composition. Normally, a sensitizer is added to the coating composition in an amount by weight from about 0.005 to about 5.0 percent by weight of the total coating composition.

Solvents useful for preparing coating compositions with the binders of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylene chloride; ethylene chloride; and the like; ethers,

such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the binders disclosed herein useful results are obtained where the photoconductive substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconductive material present can be widely varied in accordance with usual practice. It is normally required that the photoconductive material be present in an amount ranging from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductive material in the coating composition is from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a wet coating thickness in the range of about 0.001 inch to about 0.01 inch is useful in the practice of the invention. A preferred range of coating thickness is from about 0.002 inch to about 0.006 inch before drying although such thicknesses can vary widely depending on the particular application desired for the electrophotographic element.

Suitable supporting materials for coating the photoconductive layers of the present invention can include any of the electrically conducting supports, for example, paper (at a relative humidity above 20 percent); aluminumpaper laminates; metal foils, such as aluminum foil, zinc foil, etc.; metal plates, such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like conducting supports.

An especially useful conducting support can be prepared by coating a film support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. A suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer, cuprous iodide and the like. Such conducting layers and methods for their optimum preparation and use are disclosed in U.S. 3,007,901, 3,245,833 and 3,267,807.

The compositions of the present invention can be employed in photoconductive elements useful in any of the well known electrophotographic processes which require photoconductive layers. One such process is the xerographic process. In a process of this type, an electrophotographic element held in the dark, is given a blanket electrostatic charge by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means of a conventional exposure operation such as for example, by a contact-printing technique, or by lens projection of an image, or reflex or birefiex techniques and the like, to thereby form a latent electrostatic image in the photoconductive layer. Exposing the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumination in a particular area.

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charge or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of the a dust, or powder and generally comprise a pigment in a resinous carrier called a toner. A preferred method of applying such a toner to a latent electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are described in the following U.S. Pats.: 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,874,- 063; 2,984,163; 3,040,704; 3,117,884; and reissue Re. 25,779. Liquid development of the latent electrostatic image may also be used. In liquid development the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, U.S. Pat. 2,297,691 and in Australian Pat. 212,315. In dry developing processes the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powder image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after developing and fusing or fusing respectively. Techniques of the type indicated are well known in the art and have been described in a number of U.S. and foreign patents, such as US. Pats. 2,297,691 and 2,551,582, and in RCA Review, vol. 15 (1954) pages 469-484.

The compositions of the present invention can be used in electrophotographic elements having many structural variations. For example, the photoconductive composition can be coated in the form of single layers or multiple layers on a suitable opaque or transparent conducting support. Likewise, the layers can be contiguous or spaced having layers of insulating material or other photoconductive material between layers or overcoated or interposed between the photoconductive layer or sensitizing layer and the conducting layer. It is also possible to adjust the position of the support and the conducting layer placing a photoconductor layer over a support and coating the exposed face of the support or the exposed or overcoated face of the photoconductor with a conducting layer. Configurations diifering from those contained in the examples can be useful or even preferred for the same or different application for the electrophotographic element.

The following exampes are included for a further understanding of this invention.

Example 1 1.5 grams of poly[4,4'-(2-norbornylidene)bisphenoxyethyl-co-ethylene terephthalate] (Compound 6) binder containing 0.5 gram of 4,4'-benzylidene-bis'(N,N-diethylm-toluidine) photoconductor and .04 gram of 2,4-(4- ethoxyphenyl)-6-(4 n amyloxystyryl) pyryliu-rn fluoroborate sensitizer are dissolved in 15.6 grams of methylene chloride by stirring the solids in the solvent for one hour at room temperature. The resulting solution is hand coated at a wet coating thickness of 0.004 inch on a conducting layer comprising the sodium salt of a carboxyester lactone, such as described in U.S. 3,120,028, which in turn is coated on a cellulose acetate film base. The coating block is maintained at a temperature of 90 F. After drying, the electrophotographic element is charged under positive corona source until the surface potential, as measured by an electrometer probe, reaches about 600 volts. It is then subjected to exposure from behind a stepped density gray scale to a 3000 K. tungsten source. The exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential, V.,, to some lower potential, V, whose exact value depends on the actual amount of exposure in meter-candle-seconds received by the area. The results of the measurements are plotted on a graph of surface potential V vs. log exposure for each step. The shoulder speed is the numerical expression of 10 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the 600 volt charged surface potential by 100 volts. The toe speed is the numerical expression of 10 multiplied by the reciprocal of the exposure in metercandle-seconds required to reduce the 600 volt charged surface potential to 100 volts. This coating is found to have a positive 100 v. toe speed of 180. Similar results are obtained when 0.5 gram of bis(4-diethylarnino)-1,1,ltriphenylethane or 0.5 gram of bis(4-diethylamino)tetraphenylmethane are used as photoconductors in place of the 4,4-benzylidene bis(N,N-diethyl m toluidine) for both positive and negative charging.

The following Examples 2 through 5 are identical to Example 1 except that other representative binders are employed instead of Compound 6.

Coating compositions containing Compounds 1 through 4 are prepared and coated in the manner described in Example 1. In a darkened room, the surface of each of the photoconductive layers so prepared is charged to a potential of about +600 volts under a corona charger. The layer is then covered with a transparent sheet bearing a pattern of opaque and light transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about meter-candles for 12 seconds. The resulting electrostatic latent image is developed in the usual manner by cascading over the surface of the layer a mixture of negatively charged black thermoplastic toner particles and glass beads. A good reproduction of the pattern results in each instance.

Example 7 The copolyesters described herein are made by standard melt condensation techniques. Poly(4,4-isopropylidenebisphenoxypropyl-co-ethylene terephthalate), Compound l, is prepared by mixing 0.15 mole of dimethyl terephthalate, 0.075 mole of 4,4 isopropylidenebisphenoxypropanol, 0.10 mole of ethylene glycol and 0.05 gram of tetrabutyl orthotitanate. Nitrogen is bubbled through the mixture, and it is heated at 200 C. for 2 hours to distill off methanol. The temperature is raised to 250 C. and vacuum applied until polymerization is completed. The resultant polymer contains 50% of repeating unit A and 50% B. Compounds 2-21 are prepared by the same method using the appropriate bishydroxyalkyl aryl ether (see Table III below) with the desired alkylene glycol and dialkylene arylate.

TABLE III Compound number HO onioH.0 o CHzCHzOH TABLE III-Continued Cornpound number on, em nooH,oH,o oon,omon Q ason,

noomonlo Q Q-oomomon EKCHz):

CH; no cHtoHlo- -icmcmon H: h J

7 Br Br CH; 110 cmomo- 45- -o 011,011,011

| (EH: Br Br as on.

no CHmHm-Q-o-Q-OCmcHmrr noontomo- HO GH CH O- 5 0 CH1CH2OH O-CHaCHaOH The bishydroxyalkyl aryl ethers set forth in Table III are used as starting materials for the preparation of the various polymeric binders of this invention. These materials are prepared (except 22, 24 and by heating the corresponding bisphenol with a slight stoichiometric excess of ethylene carbonate at a temperature from about 100 C. to about 300 C. in the presence of an alkali metal hydroxide or alkali metal carbonate catalyst. Typisodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, etc. Reaction time general- 1y varies from 0.1 to about 50 hours or more. Catalyst concentration generally ranges from 0.1 gram of catalyst for each gram of carbonate to about 0.0001 gram of catalyst per gram of carbonate. The product obtained need not be purified for the preparation of the polyester binders described herein. A typical preparation is set forth in Excal catalysts include lithium hydroxide, lithium carbonate, ample 8.

Example 8 prising a random, linear co-polyester having 280% re- A mixture of 0.10 mole of 4,4'-isopropylidenebis-2- Peating units of:

methylphenol, 0.21 mole of ethylene carbonate and 20 o mg. of lithium hydroxide is heated under nitrogen at 190 I1 I C. for 6 hours. The reaction product is found to be 4,4'- j" isopropylidenebis 2 methylphenoxyethanol (Compound 25). together with 20-98% repeating units of Example 9 wherein Compound 22 is prepared by the addition of 3-bromol-propanol to a refluxing aqueous ethanolic solution of the disodium salt of 4,4-isopropylidenediphenol. After 6 hours, the product is mixed with ethyl ether and washed with a 10% sodium hydroxide solution. The product is isolated by evaporation.

D is selected from the group consisting of (a) an aliphatic alkyl radical having 1 to 4 carbon atoms, (b) when joined with E, a monocycloalkylidene nucleus of 5 to 6 carbon atoms, (c) when joined with E, a norbornylidene nucleus; Example 10 E is selected from the group consisting of Compound 24 is prepared by heating 4,4'-isopropyl- (a) a yl halPPhenyl radical idenediphenol with propylene oxide in the presence of (b) when lomed Wlth monocycloalkyhdene sodium methoxide and benzyltrimethylarnmonium hynucleus of 5 to 6 carbon atoms droxide as described in Example 3 of U.S. Patent z g ig joined with a norbornylidene Example 11 X is a phenylene group;

G, L, G, and L' are each selected from the group Compound 35 is prepared by reacting phenol with pconsisting of mentha-1,5-diene in the manner described in C.A. 68 li h i lk l di l f1 4 b t 59271. (b) hydrogen,

The invention has been described in detail with particu- (c) a h l atom, lar reference to preferred embodiments thereof but it will Z i an lk l di l h i 2 t 4 carbon atoms be understood that variations and modifications can be 3 The electrophotographic element f l i 2 wheree t d Within the Spirit and Scope of the invention in the sensitizer is selected from the group consisting of I claim: cyanine and pyrylium dye salts.

Anfilecfi'ophotographlc element pl' g a i}- 4. The electrophotographic element of claim 2 where- P having Coated ihfireon a photocoflductlve 9011113051 in the binder is poly(4,4'-isopropylidenebis-Z-methylphention comprising a photoconductor and a binder for said oxyethypcmethylene terephtha1ate) photpcondlgcwr comprlsmg a Polyester havmg 280% 5. The electrophotographic element of claim 2 wherein peating units of: the binder is poly[4,4'-(l-phenylethylidene)bisphcnoxyo 0 ethyl-co-ethylene terephthalate]. 6. The electrophotographic element of claim 2 wherein L the binder is poly[4,4'-(2-norb0rnylidene)bisphenoxytogether with 20-98% repeating units of ethyl-co-ethylelle terephthalatel- 0 r G G r 1 '-CH2CH2 O@ ?--O-CH2CHz-OC-XC-o L E J L L wherein 7. The electrophotographic element of claim 2 where- D is selected from the group consisting of in the binder is poly{4,4'-[l-(p-bromophenyl)ethyli- (a) an aliphatic alkyl radical having 1 to 4 cardene]-bisphenoxyethyl-co-ethylene terephthalate}.

bon atoms, 8. An electrophotographic element comprising a sup- (b) when joined with E, a monocycloalkylidene port having coated thereon a photoconductive composinucleus of 5 to 6 carbon atoms, tion comprising 10 to about weight percent of 4,4- (c) when joined with E, a norbornylidene nucleus; benzylidene bis(N,N-diethyl-m-toluidine) as an organic E is selected from the group consisting of photoconductor, 0.005 to about 5.0 weight percent of a (a) a phenyl or halophenyl radical, 60 sensitizer for said photoconductor and poly(4,4'-iso- (b) when joined with D, a monocycloalkylidene propylidenebis-2-methylphenoxyethyl-co-ethylene terephnucleus, of 5 to 6 carbon atoms, thalate). (c) when joined with D, a norbornylidene 9. An electrophotographic element comprising a supnucleus; port having coated thereon a photoconductive composi- X is a phenylene group; 5 tion comprising 10 to about 60 weight percent of 4,4- G, L, G, and L, are each selected from the group benzylidencbis(N,N-diethyl-m-toluidine) as an organic consisting of photoconductor, 0.005 to about 5.0 weight percent of a (a) an aliphatic alkyl radical of 1 4 carbon atoms, t z r f a d PhOtOCOHdUCtOI' and P Y[ (b) hydrogen, phenylethylidene)bisphenoxyethyl co ethfiene tereph- (c) a halogen atom; thalate]. Z is an alkylene radical having 2 to 4 carbon atoms. 10. An electrophotographic element comprising a sup- 2. An electrophotographic element comprising a support having coated thereon a photoconductive composiport having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4- tion comprising an organic photoconductor, a sensitizer benzyli enebi (N,N-diethyl-m-toluidine) as an organic and a binder for said photoconductor and sensitizer, comphotoconductor, 0.005 to about 5.0 weight percent of a 25 sensitizer for said photoconductor and poly[4,4'-(2-norbornylidene)bisphenoxyethyl-co-ethylene terephthalate].

11. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4-benzy1- idenebis(N,N-diethyl-m-toluidine) as an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and po1y{4,4'-[1(p-bromophenyl)ethylidene] bisphenoxyethyl-co-ethylene terephthalate}.

12. In an electrophotographic process wherein an electrostatic charge pattern is formed on an electrophotographic element, by applying a uniform charge to the surface of the photoconductive layer and exposing to a light image the improvement characterized in that said electrographic element has a photoconductive layer containing a binder having 2-80% repeating units of:

together with 20-98% repeating unit of wherein D is selected from the group consisting of (a) an aliphatic alkyl radical having 1 to 4 carbon atoms, (b) when joined with E, a monocycloalkylidene nucleus of 5 to 6 carbon atoms, (0) when joined with E, a norbornylidene nucleus; E is selected from the group consisting of (a) a phenyl or halophenyl radical, (b) when joined with D, a monocycloalkylidene nucleus of 5 to 6 carbon atoms, (0) when joined with D, a norbornylidene nucleus; X is a phenylene group; G, -L, G, and L are each selected from the group consisting of (a) an aliphatic alkyl radical of 1-4 carbon atoms, (b) hydrogen, (c) a halogen atom, Z is an alkylene radical having 2 to 4 carbon atoms.

References Cited UNITED STATES PATENTS 3,118,785 1/1964 Anderson et a1. 260-47 C 3,159,483 12/1964 Behmenburg et al. 961.5 3,197,307 7/1965 Blake et al. 961.8 3,216,970 11/1965 Conix 260-47 C 3,259,816 7/1966 Katchman 260-47 C 3,265,496 8/1966 Fox 96-1.5 3,387,973 6/1968 Fox et al. 96-15 3,403,132 9/1968 Waller 260-47 C 3,526,501 9/1970 Fox 96-15 3,615,406 10/1971 Merrill 96-15 OTHER REFERENCES Neuman: The Science and Art of Xerography, Part I, The British Journal of Photography (September 1964) Conix, Andr: Thermoplastic Polyesters from Bisphenols, Industrial and Engineering Chemistry, vol. 51, No. 2, pp. 147-150 (February 1959).

CHARLES L. VAN HORN, Primary Examiner US. Cl. X.R. 

